CVE-2026-55737 Erlang CVE debrief

Who should care

Users of Erlang OTP erts, particularly those using versions from OTP 25.0 before OTP 29.0.4, OTP 28.5.0.4 and OTP 27.3.4.15, should be aware of this vulnerability and take necessary precautions. Operators, platform administrators, vulnerability management teams, and security teams should review the official advisory and assess their exposure.

Technical summary

The vulnerability occurs when decoding a LARGE_TUPLE_EXT term. The validation pass decoded_size() in erts/emulator/beam/external.c reads the 32-bit arity field as unsigned (get_uint32()), while the decode pass dec_term() reads the same field as a signed 32-bit integer (get_int32()) into an int. An arity wire value of 0x80000000 passes validation as 2147483648 but decodes as -2147483648, causing the heap allocation pointer to move backward. This results in an out-of-bounds heap write. The required padding is large when uncompressed but the compressed-ETF envelope shrinks it to a small payload on the wire.

Defensive priority

High

Recommended defensive actions

• Update to OTP 29.0.4, OTP 28.5.0.4, or OTP 27.3.4.15
• Restrict access to the affected systems
• Monitor for suspicious activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-27T16:17:48.847Z and has not been modified since then. The NVD entry is currently Received. There is limited information available about the vulnerability, and defenders should verify the affected scope and severity with the official advisory.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.