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EUVD-2026-329192

fkie_cve-2026-54236

vLLM is an inference and serving engine for large language models (LLMs). Prior to 0.23.1rc0, the fix for CVE-2026-22778, which introduced a sanitize_message helper that strips object-repr memory addresses from error messages before they reach the client, is incomplete: several response paths echo str(exc) directly to clients without calling sanitize_message. The unsanitized sites include the Anthropic API router in vllm/entrypoints/anthropic/api_router.py (the POST /v1/messages and POST /v1/messages/count_tokens handlers), the Server-Sent Events streaming converter in vllm/entrypoints/anthropic/serving.py, and the realtime speech-to-text WebSocket in vllm/entrypoints/speech_to_text/realtime/connection.py. These paths catch the exception inside the route coroutine and construct the JSONResponse themselves, bypassing the sanitizing global FastAPI exception handler, and WebSocket frames do not traverse that handler chain at all. Using the same primitive as the parent issue, an unauthenticated attacker can send malformed image bytes through the Anthropic Messages API image content parts so that PIL.Image.open raises an UnidentifiedImageError whose message contains the BytesIO object repr, leaking the heap memory address verbatim in the error.message field of the response body. This vulnerability is fixed in 0.23.1rc0.

GHSA-hgg8-fqqc-vfmw — vLLM: incomplete CVE-2026-22778 fix leaks PIL repr addresses via Anthropic router

Affected: PyPI: vllm

# vLLM: incomplete CVE-2026-22778 fix leaks PIL repr addresses via the Anthropic API router

**Researcher:** Kai Aizen — SnailSploit (@SnailSploit), Adversarial & Offensive Security Research **Severity:** CVSS 3.1 5.3 (Medium) `AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N` **Target:** https://github.com/vllm-project/vllm

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## Summary

The fix for CVE-2026-22778 / GHSA-4r2x-xpjr-7cvv (PRs #31987 and #32319) introduced `sanitize_message` and applied it at four FastAPI exception-handling sites in the OpenAI router. The sanitizer strips object-repr memory addresses (`<_io.BytesIO object at 0x7a95e299e750>` → `<_io.BytesIO object>`) before error messages reach the client, defeating the ASLR-bypass primitive that CVE-2026-22778 chained with a libopenjp2 heap overflow for RCE.

The fix is incomplete: response paths added to vLLM at or after the same time as the fix continue to echo `str(exc)` directly to clients without `sanitize_message`. The original Stage 1 primitive — sending malformed image bytes so PIL raises `UnidentifiedImageError` whose message contains the BytesIO object repr — reaches all of them unmodified and leaks the heap address verbatim in the response body.

All five lines below are present in `main` HEAD (`771e1e48b`, 2026-05-26).

## Affected sites

Current `main` HEAD (`771e1e48b`, 2026-05-26):

| # | File | Line | Code | |---|---|---|---| | 1 | `vllm/entrypoints/anthropic/api_router.py` | 78 | `message=str(e),` (inside `POST /v1/messages` exception handler) | | 2…

PYSEC-2026-3408 — vLLM: incomplete CVE-2026-22778 fix leaks PIL repr addresses via Anthropic router