CVE-2026-59248
Remote memory-exhaustion DoS in cowlib HPACK/QPACK integer decoder
Is CVE-2026-59248 being exploited?
Not confirmed. CVE-2026-59248 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.29% probability of exploitation in the next 30 days.
How severe is CVE-2026-59248?
CVE-2026-59248 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-59248?
Yes. A fix has been recorded for CVE-2026-59248. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-59248 affect?
CVE-2026-59248 affects cowlib versions >=2.0.0 and <2.19.0, Cowboy (HTTP server), RabbitMQ management plugin, Other Erlang/Elixir HTTP/2 and HTTP/3 servers/clients. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-59248?
Upgrade cowlib to >=2.19.0; update Cowboy/RabbitMQ; block/untrusted HTTP/2/3 or rate-limit ingress.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated HTTP/2/3 peers can force huge bignum allocations, exhausting Erlang VM memory and causing denial of service.
Immediate action required
- affected>= 2.0.0-pre.1 and < 2.19.0
- affected>= 5ddecbc121f812aec53d9df91829448d8e94e44c and < f582430498072a0c65ad338030321576dc13a343
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.