CVE-2021-26953 is a high-severity (CVSS 7.5) CWE-908 vulnerability in postscript. 1 public exploit reference exists, so weaponization risk is real. A fix is available for postscript — see the affected versions and patch details below.
Read on uninitialized buffer in postscript
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-26953 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
postscriptReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Affected versions of this crate passes an uninitialized buffer to a user-provided Read implementation.
Arbitrary Read implementations can read from the uninitialized buffer (memory exposure) and also can return incorrect number of bytes written to the buffer. Reading from uninitialized memory produces undefined values that can quickly invoke undefined behavior.
This flaw was fixed in commit 8026286 by zero-initializing the buffer before handing to a user-provided Read.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | postscript | all versions | 0.14.0cargo update -p postscript --precise 0.14.0 |
Affected Products
postscriptpostscript_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for postscript, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update postscript to 0.14.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-26953 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2021-26953 in your dependencies?
Find it across crates.io, including transitive dependencies.