# CVE-2026-128238: Scapy before 2.8.0 Uncontrolled Recursion DoS via BER SEQUENCE Decoder

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

Scapy before 2.8.0 contains an uncontrolled recursion vulnerability in the BER/ASN.1 decoder in scapy/asn1/ber.py that allows unauthenticated remote attackers to crash parsing applications. Attackers can send a single 833-byte packet with 250 nested ASN.1 SEQUENCE structures to trigger an unhandled RecursionError, terminating TLS, SNMP, X.509, or LDAP parsers even with safe=True.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- secdev / scapy (scapy): ≥ 0; < 2.8.0 (affected, semver); 2.8.0 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: VulnCheck

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-674

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/secdev/scapy/security/advisories/GHSA-456h-w4v7-hvpr (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/scapy-before-2.8.0-uncontrolled-recursion-dos-via-ber-sequence-decoder (CNA: VulnCheck; third-party-advisory)

- https://github.com/secdev/scapy/security/advisories/GHSA-456h-w4v7-hvpr (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/scapy-before-2.8.0-uncontrolled-recursion-dos-via-ber-sequence-decoder (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-128238; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-128238; retrieved 2026-11-13; source updated 2026-11-13

Revision: 64dae0d3f9679411020f8283bc7a6c656e5e8a5c96538767c7018a171df37710

Canonical: https://y2.dev/cve/CVE-2026-128238

## Agent and API access

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- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

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- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

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