EUVD-2026-49739
GHSA-f37p-pc7r-rghm
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Primary rating from Vendor (6b3ad84c-e1a6-4bf7-a703-f496b71e49db).
CVSS VectorVendor: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Lifecycle Timeline
4DescriptionCVE.org
Allocation of resources without limits vulnerability in ninenines cowlib allows an unauthenticated remote HTTP/2 or HTTP/3 peer to exhaust memory on the vulnerable server (or client) and cause a denial of service.
The HPACK and QPACK prefixed-integer decoder cow_hpack_common:dec_big_int/3 in src/cow_hpack_common.hrl (invoked from cow_hpack:decode/2 in src/cow_hpack.erl and from cow_qpack:decode_field_section/3 in src/cow_qpack.erl) reads continuation octets until it sees one whose high bit is clear, evaluating Int + (Value bsl M) at each step with the shift M growing by seven per octet. No limit is enforced on the number of continuation octets, on the resulting bit width, or on the value; the decoder consumes whatever encoded length the peer supplies.
Because Erlang integers are immutable, each intermediate Value bsl M and each accumulator update allocates a fresh bignum whose digit width grows linearly with the number of octets processed so far. Summed across the whole decode, the transient bignum digit materialization is on the order of the square of the encoded length. A single maximal HPACK indexed representation carried inside one HTTP/2 HEADERS plus one CONTINUATION frame at Cowboy's default max_frame_size_received can force hundreds of megabytes of transient allocation and garbage-collection churn before the resulting header-table index is rejected as invalid. Repeated or concurrent connections multiply the pressure and can drive the Erlang VM to memory exhaustion.
Cowlib is the HTTP parser used by Cowboy, RabbitMQ's management plugin, and other Erlang and Elixir HTTP/2 and HTTP/3 servers and clients, so any exposed endpoint that accepts HPACK or QPACK from an untrusted peer is reachable.
This issue affects cowlib: from 2.0.0 before 2.19.0.
AnalysisAI
We need to produce a JSON analysis for CVE-2026-59248 based on the provided data. The input includes a description, CVSS 4.0 vector, CWE, tags, references, and source code evidence. We'll extract information accordingly.
The CVE ID is CVE-2026-59248. Product: cowlib (but description says "ninenines cowlib", actually "cowlib" is the library name by ninenines). The product name should be the specific product affected: cowlib. So product_name: "cowlib". Could also be "cowlib HTTP parser". Keep short, 1-3 words. "cowlib" works.
Summary: Original synthesis. Mention that HPACK/QPACK integer decoding in cowlib lacks limits, allowing remote unauthenticated attacker to exhaust memory via HTTP/2 or HTTP/3, causing DoS. Impact: memory exhaustion, Erlang VM crash. Mention if actively exploited? No KEV data, no POC explicitly stated, but the description suggests it's easy to trigger. EPSS not provided (none given). So we can say "no public exploit identified". Need to note EPSS unknown. Since EPSS not in data, we can't assess its probability. But we can say EPSS data not available. So summary: "Memory exhaustion in ninenines cowlib 2.0.0 before 2.19.0 allows remote unauthenticated HTTP/2 or HTTP/3 attackers to exhaust server memory and cause denial of service via crafted HPACK/QPACK integers." That's a concise summary.
Technical context: Explain underlying tech: HPACK (HTTP/2 header compression) and QPACK (HTTP/3), integer decoding with variable-length encoding using prefixed integers. Erlang's immutable integers cause bignum allocations with growing size, quadratic memory allocation from many continuation octets. CWE-770: Allocation of Resources Without Limits. Affects cowlib, used by Cowboy, RabbitMQ management plugin, etc. Give context.
Risk assessment: CVSS 4.0: 8.7, AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H (VA:H implies high availability impact on vulnerable system). No EPSS score. No KEV. No POC? At least not in provided data; but the commit adds a test that triggers it
Same technique Denial Of Service
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