{"id":"CVE-2026-94450","kind":"vulnerability","aliases":["CVE-2026-94450"],"related":[],"title":"s2n-quic: crafted UDP packet shuts down Retry-configured QUIC servers","description":"CVE-2026-94450 - Potential denial of service when configured to send Retry packets in s2n-quic\n\n### CVE-2026-94450 - Potential denial of service when configured to send Retry packets in s2n-quic\n\nBulletin ID: 2026-116-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 09/22/2026 13:00 PM PDT\n\nDescription:\n\ns2n-quic is a Rust implementation of the QUIC protocol. We identified CVE-2026-94450, an issue with improper validation of the Destination Connection ID length when a server is configured to send Retry packets. s2n-quic 1.88.0 and earlier allow an unauthenticated user to shut down a server endpoint via a single crafted UDP datagram. No AWS services are affected by this issue, and customers of AWS services do not need to take action. Only server endpoints specifically configured to issue Retry packets are affected.\n\nImpacted versions: <= v1.88.0\n\nResolution:\n\nThis issue has been addressed in s2n-quic version 1.89.0. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.\n\nWorkarounds:\n\nThere is no workaround that mitigates this issue. Upgrading to the patched version is the recommended remediation.\n\nReferences:\n\n- CVE-2026-94450\n- GHSA-5rw2-6x5m-v22x\n\n Please email aws-security@amazon.com with any security questions or concerns.","summary":"s2n-quic, AWS's Rust implementation of QUIC, does not properly validate the Destination Connection ID length when a server is set to send Retry packets. A single crafted UDP datagram from an unauthenticated sender shuts down that server endpoint.","severity":"high","cvss":8.7,"epss":0.01944,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["aws","lab-disclosure","package","quic","rust","s2n-quic","self-hosted"],"not_affected_if":["aws-managed-services","client-only","default-config"],"how_to_check":"- Check the s2n-quic version in `Cargo.lock` with `grep -A1 'name = \"s2n-quic\"' Cargo.lock`; affected is `<= 1.88.0`\n- Check whether the server sets Retry packets, e.g. `grep -rn 'retry' src/` for a Retry token provider or Retry configuration in the QUIC endpoint setup","fix":"- Upgrade s2n-quic to `1.89.0` or later with `cargo update -p s2n-quic`\n- Patch any forked or vendored copy of s2n-quic to include the fix\n- No workaround exists; upgrading is the only remediation","status":"open","published_at":"2026-09-22T00:00:00+00:00","first_seen_at":"2026-10-24T19:28:16+00:00","triaged_at":"2026-10-25T05:29:31+00:00","updated_at":"2026-10-25T12:38:49+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-10-25T05:29:31Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade s2n-quic to `1.89.0` or later with `cargo update -p s2n-quic`\n- Patch any forked or vendored copy of s2n-quic to include the fix\n- No workaround exists; upgrading is the only remediation","reach":"internet","title":"s2n-quic: crafted UDP packet shuts down Retry-configured QUIC servers","impact":"medium","summary":"s2n-quic, AWS's Rust implementation of QUIC, does not properly validate the Destination Connection ID length when a server is set to send Retry packets. A single crafted UDP datagram from an unauthenticated sender shuts down that server endpoint.","category":"package","nicknames":[],"who_cares":["rust","s2n-quic","quic","self-hosted"],"confidence":0.8,"needs_auth":"no","worst_case":"Unauthenticated attacker shuts down the QUIC server endpoint with one datagram","analyst_note":"","how_to_check":"- Check the s2n-quic version in `Cargo.lock` with `grep -A1 'name = \"s2n-quic\"' Cargo.lock`; affected is `<= 1.88.0`\n- Check whether the server sets Retry packets, e.g. `grep -rn 'retry' src/` for a Retry token provider or Retry configuration in the QUIC endpoint setup","needs_analyst":false,"not_affected_if":["aws-managed-services","default-config","client-only"],"who_is_affected":"Only servers that use s2n-quic and are specifically configured to issue Retry packets are exposed, and the attacker needs only to send one UDP datagram. AWS services are not affected and AWS customers do not need to act. Teams running their own QUIC servers on s2n-quic 1.88.0 or earlier, including forks, should check.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000707,"input_tokens":3802,"output_tokens":654,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-116':111C '-2026':15A,18A,75C,92C,142C,272C '-94450':16A,19A,76C,93C,143C,273C '00':124C '09/22/2026':122C '1.88.0':167C '1.89.0':230C '13':123C '2026':110C '5rw2':276C '6x5m':277C 'action':204C 'address':224C 'affect':190C,215C 'allow':170C 'attent':119C 'aw':20B,36B,112C,114C,187C,197C 'aws-security@amazon.com':281C 'bulletin':108C 'code':244C 'concern':287C 'configur':11A,82C,99C,159C,209C 'connect':48B,152C 'content':115C 'craft':4A,62B,183C 'custom':195C 'cve':14A,17A,74C,91C,141C,271C 'datagram':64B,185C 'date':121C 'denial':78C,95C 'deriv':243C 'descript':127C 'destin':47B,151C 'disclosur':23B 'earlier':169C 'email':280C 'endpoint':73B,179C,207C 'ensur':239C 'fix':251C 'fork':241C 'ghsa':275C 'ghsa-5rw2-6x5m-v22x':274C 'host':32B 'id':49B,109C,153C 'identifi':140C 'impact':216C 'implement':39B,134C 'import':117C 'improp':147C 'incorpor':248C 'issu':145C,193C,211C,221C,260C 'lab':22B 'lab-disclosur':21B 'latest':236C 'length':50B,154C 'mitig':258C 'need':201C 'new':250C 'packag':24B 'packet':6A,59B,86C,103C,163C,213C 'patch':246C,264C 'pdt':126C 'pleas':279C 'pm':125C 'potenti':77C,94C 'proper':44B 'protocol':138C 'public':120C 'question':285C 'quic':3A,12A,25B,29B,35B,41B,90C,107C,130C,137C,166C,228C 'recommend':232C,268C 'refer':270C 'remedi':269C 'requir':118C 'resolut':219C 'retri':10A,58B,85C,102C,162C,212C 'retry-configur':9A 'rust':26B,38B,133C 's2n':2A,28B,34B,89C,106C,129C,165C,227C 's2n-quic':1A,27B,33B,88C,105C,128C,164C,226C 'scope':113C 'secur':284C 'self':31B 'self-host':30B 'send':57B,84C,101C,161C 'sender':68B 'server':13A,53B,72B,157C,178C,206C 'servic':80C,97C,188C,198C 'set':55B 'shut':7A,69B,175C 'singl':61B,182C 'specif':208C 'take':203C 'type':116C 'udp':5A,63B,184C 'unauthent':67B,172C 'upgrad':233C,261C 'user':173C 'v1.88.0':218C 'v22x':278C 'valid':45B,148C 'version':217C,229C,237C,265C 'via':180C 'workaround':252C,256C","nicknames":[],"mitigations":[],"who_affected":"Only servers that use s2n-quic and are specifically configured to issue Retry packets are exposed, and the attacker needs only to send one UDP datagram. AWS services are not affected and AWS customers do not need to act. Teams running their own QUIC servers on s2n-quic 1.88.0 or earlier, including forks, should check.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-09-22T00:00:00+00:00","kev":null,"cvss_vector":"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","cvss_by":"ff89ba41-3aa1-4d27-914a-91399e9639e5","poc_count":0,"sources":[{"source":"lab","external_id":"https://aws.amazon.com/security/security-bulletins/rss/2026-116-aws/#CVE-2026-94450","url":"https://aws.amazon.com/security/security-bulletins/rss/2026-116-aws/","severity":null,"published_at":"2026-09-22T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-24T19:28:16+00:00","fetched_at":"2026-10-25T08:14:50+00:00","note":"AWS: CVE-2026-94450 - Potential denial of service when configured to send Retry packets in s2n-quic"},{"source":"nvd","external_id":"CVE-2026-94450","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-94450","severity":null,"published_at":"2026-09-22T21:17:33+00:00","modified_at":"2026-10-20T19:19:24+00:00","first_seen_at":"2026-10-24T20:15:27+00:00","fetched_at":"2026-10-24T20:15:27+00:00","note":null},{"source":"epss","external_id":"CVE-2026-94450","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-94450","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-25T12:38:49+00:00","fetched_at":"2026-10-25T12:38:49+00:00","note":null}],"documents":[{"id":2948,"url":"https://aws.amazon.com/security/security-bulletins/rss/2026-116-aws/","title":"AWS: CVE-2026-94450 - Potential denial of service when configured to send Retry packets in s2n-quic","kind":"advisory","source":"lab","text":"CVE-2026-94450 - Potential denial of service when configured to send Retry packets in s2n-quic\n\n### CVE-2026-94450 - Potential denial of service when configured to send Retry packets in s2n-quic\n\nBulletin ID: 2026-116-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 09/22/2026 13:00 PM PDT\n\nDescription:\n\ns2n-quic is a Rust implementation of the QUIC protocol. We identified CVE-2026-94450, an issue with improper validation of the Destination Connection ID length when a server is configured to send Retry packets. s2n-quic 1.88.0 and earlier allow an unauthenticated user to shut down a server endpoint via a single crafted UDP datagram. No AWS services are affected by this issue, and customers of AWS services do not need to take action. Only server endpoints specifically configured to issue Retry packets are affected.\n\nImpacted versions: <= v1.88.0\n\nResolution:\n\nThis issue has been addressed in s2n-quic version 1.89.0. We recommend upgrading to the latest version and ensuring any forked or derivative code is patched to incorporate the new fixes.\n\nWorkarounds:\n\nThere is no workaround that mitigates this issue. Upgrading to the patched version is the recommended remediation.\n\nReferences:\n\n- CVE-2026-94450\n- GHSA-5rw2-6x5m-v22x\n\n Please email aws-security@amazon.com with any security questions or concerns.","published_at":"2026-09-22T00:00:00+00:00","relation":"advisory","confidence":null,"note":null}],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}