GHSA-hm4w-wwcw-mr6r is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in pyasn1. O3 Security confirms whether GHSA-hm4w-wwcw-mr6r is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
pyasn1: Uncontrolled resource consumption when converting decoded REAL values
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-hm4w-wwcw-mr6r.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-hm4w-wwcw-mr6r plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
pyasn1Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
The univ.Real type converted its (mantissa, base, exponent) value to a Python float using exact big-integer exponentiation. A BER/CER/DER-encoded REAL value only a few bytes long can carry a very large exponent, causing this computation to attempt to materialize an astronomically large integer.
Any operation that triggers float conversion on such a decoded value — prettyPrint(), str(), comparison, arithmetic, or an explicit float() call — consumes excessive CPU and memory, hanging the process. Applications that decode untrusted ASN.1 data and then print, log, or compare the decoded objects are vulnerable to denial of service. Decoding alone does not trigger the issue.
Affected components
- pyasn1.type.univ.Real — float conversion (float() and everything built on it: prettyPrint(), str(), comparisons, arithmetic, int())
- Reachable through the pyasn1.codec.ber, cer, and der decoders, which produce Real objects from untrusted input; also via directly constructed Real values
The encoders and the native codec are not affected. Applications that never handle ASN.1 REAL values are not affected.
Patches
Fixed in pyasn1 0.6.4. Binary (base-2) values are now converted with math.ldexp(), and decimal (base-10) values with exponents beyond float range raise OverflowError without constructing huge intermediate integers. Existing behavior is preserved: out-of-range values raise OverflowError and prettyPrint() renders them as <overflow>.
Workarounds
Avoid converting, printing, or comparing decoded Real objects from untrusted sources; inspect the raw (mantissa, base, exponent) tuple instead.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyasn1 | all versions | 0.6.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyasn1. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update pyasn1 to 0.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hm4w-wwcw-mr6r 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.
How O3 protects you
O3 pinpoints whether GHSA-hm4w-wwcw-mr6r is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-hm4w-wwcw-mr6r. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This flaw in pyasn1, rated as Important, could lead to a denial of service in Red Hat products that process untrusted ASN.1 data. A remote attacker could send a specially crafted BER, CER, or DER encoded REAL value with a large exponent, causing applications to consume excessive resources during decoding operations…
Frequently Asked Questions
Is GHSA-hm4w-wwcw-mr6r in your dependencies?
O3 detects GHSA-hm4w-wwcw-mr6r across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.