CVE-2026-59248: Unbounded HPACK/QPACK prefixed-integer decoding in Cowlib causes memory-exhaustion DoS
CSIRTS triage
- What
- Unbounded HPACK/QPACK prefixed-integer decoding allows attackers to exhaust memory through integer parsing.
- Who is affected
- HTTP/2 and QUIC applications using Cowlib for header compression.
- Urgency
- Unknown severity; memory exhaustion DoS is a denial-of-service risk requiring immediate attention.
- Action
- Update Cowlib to version with bounded integer decoding.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59248
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-592480.29% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 22% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-59248 | coverage & exploitation status | NVD · CVE.org |
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