{"id":"CVE-2026-48747","aliases":["DEBIAN-CVE-2026-48747","EUVD-2026-44375","GHSA-rrj9-5q2j-4gvr","UBUNTU-CVE-2026-48747"],"status":"published","title":"Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","severity":{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00247,"percentile":0.1608,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-347","CWE-757"],"published":"2026-06-15T17:32:28Z","modified":"2026-10-28T02:30:36Z","fixes":[{"ecosystem":"Packagist","package":"symfony/mailomat-mailer","fixed_in":["7.4.13","8.0.13"],"sources":["ghsa","osv"]},{"ecosystem":"Packagist","package":"symfony/symfony","fixed_in":["7.4.13","8.0.13"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"symfony","fixed_in":["7.4.13+dfsg-1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"symfony/mailomat-mailer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.4.13"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"symfony/mailomat-mailer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.13"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"symfony/symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.4.13"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"symfony/symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.13"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.4.13+dfsg-1"}]}],"versions":["6.4.21+dfsg-2","6.4.24+dfsg-1","6.4.25+dfsg-1","7.0.4+dfsg-1","7.0.5+dfsg-1","7.0.6+dfsg-1","7.0.7+dfsg-1","7.1.0~beta1+dfsg-1","7.1.0~rc1+dfsg-1","7.1.2+dfsg-1","7.1.3+dfsg-1","7.1.4+dfsg-1","7.1.5+dfsg-1","7.2.0~beta1+dfsg-1","7.2.0~beta2+dfsg-1","7.2.0~rc1+dfsg-1","7.2.1+dfsg-1","7.2.2+dfsg-1","7.2.3+dfsg-1","7.2.4+dfsg-1","7.2.5+dfsg-1","7.2.6-1","7.3.0+dfsg-1","7.3.0~beta1+dfsg-1","7.3.0~beta2+dfsg-1","7.3.0~rc1+dfsg-1","7.3.1+dfsg-1","7.3.2+dfsg-1","7.3.3+dfsg-1","7.3.4+dfsg-1","7.3.5-1","7.4.0+dfsg-1","7.4.0+dfsg-2","7.4.0~beta1-1","7.4.0~beta1-2","7.4.0~beta2+dfsg-1","7.4.0~beta2+dfsg-2","7.4.0~beta2+dfsg-3","7.4.0~rc1+dfsg-1","7.4.0~rc2+dfsg-1","7.4.0~rc3+dfsg-1","7.4.10+dfsg-1","7.4.12+dfsg-1","7.4.2+dfsg-1","7.4.2+dfsg-2","7.4.3+dfsg-1","7.4.4+dfsg-1","7.4.5+dfsg-1","7.4.6+dfsg-1","7.4.6+dfsg-2","7.4.7+dfsg-1","7.4.8+dfsg-1","7.4.9+dfsg-1"]},{"source":"osv","ecosystem":"Packagist","package":"symfony/mailomat-mailer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.4.13"}]}],"versions":["v7.2.0","v7.3.0","v7.3.0-BETA1","v7.3.0-RC1","v7.4.0","v7.4.0-BETA1","v7.4.0-RC1"]},{"source":"osv","ecosystem":"Packagist","package":"symfony/mailomat-mailer","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.13"}]}],"versions":["v8.0.0"]},{"source":"osv","ecosystem":"Packagist","package":"symfony/symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.4.13"}]}],"versions":["v7.2.0","v7.2.1","v7.2.2","v7.2.3","v7.2.4","v7.2.5","v7.2.6","v7.2.7","v7.2.8","v7.2.9","v7.3.0","v7.3.0-BETA1","v7.3.0-BETA2","v7.3.0-RC1","v7.3.1","v7.3.10","v7.3.11","v7.3.2","v7.3.3","v7.3.4","v7.3.5","v7.3.6","v7.3.7","v7.3.8","v7.3.9","v7.4.0","v7.4.0-BETA1","v7.4.0-BETA2","v7.4.0-RC1","v7.4.0-RC2","v7.4.0-RC3","v7.4.1","v7.4.10","v7.4.11","v7.4.12","v7.4.2","v7.4.3","v7.4.4","v7.4.5","v7.4.6","v7.4.7","v7.4.8","v7.4.9"]},{"source":"osv","ecosystem":"Packagist","package":"symfony/symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.13"}]}],"versions":["v8.0.0","v8.0.1","v8.0.10","v8.0.11","v8.0.12","v8.0.2","v8.0.3","v8.0.4","v8.0.5","v8.0.6","v8.0.7","v8.0.8","v8.0.9"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.7.1+dfsg-1","2.7.5+dfsg-1","2.7.9+dfsg-1","2.7.9+dfsg-1ubuntu2","2.7.10-0ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.8.7+dfsg-1.3ubuntu1","3.4.3+dfsg-1ubuntu4","3.4.6+dfsg-1","3.4.6+dfsg-1ubuntu0.1","3.4.6+dfsg-1ubuntu0.1+esm1","3.4.6+dfsg-1ubuntu0.1+esm2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.3.4+dfsg-1ubuntu1","4.3.8+dfsg-1ubuntu1","4.3.8+dfsg-1ubuntu1+esm1","4.3.8+dfsg-1ubuntu1+esm2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:22.04:LTS","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.6+dfsg-1ubuntu7","5.4.4+dfsg-1ubuntu8","5.4.4+dfsg-1ubuntu8+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:24.04:LTS","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.4.23+dfsg-1ubuntu1","5.4.35+dfsg-3ubuntu1","6.4.5+dfsg-3ubuntu2","6.4.5+dfsg-3ubuntu3","6.4.5+dfsg-3ubuntu3+esm1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.4.18+dfsg-1ubuntu1","6.4.21+dfsg-2","6.4.21+dfsg-2ubuntu1","6.4.24+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.4.7+dfsg-1ubuntu1","7.4.9+dfsg-1ubuntu1","7.4.13+dfsg-2ubuntu1","7.4.14+dfsg-1ubuntu2","7.4.15+dfsg-2ubuntu2","7.4.16+dfsg-1ubuntu2"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"symfony","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.4.24+dfsg-1","7.4.5+dfsg-1ubuntu1","7.4.6+dfsg-2ubuntu1","7.4.7+dfsg-1ubuntu1"]}],"products":[{"vendor":"sensiolabs","product":"symfony"},{"vendor":"symfony","product":"mailomat-mailer"},{"vendor":"symfony","product":"symfony"}],"references":[{"url":"https://github.com/symfony/symfony/security/advisories/GHSA-rrj9-5q2j-4gvr","tags":["x_refsource_CONFIRM","Patch","Vendor Advisory","advisory","web"]},{"url":"https://github.com/symfony/symfony/commit/bdfe9fe0d94d33dfaca0bc2fe0b00b54767b0c88","tags":["x_refsource_MISC","Patch","fix","web","report"]},{"url":"https://github.com/symfony/symfony/releases/tag/v7.4.13","tags":["x_refsource_MISC","Product","Release Notes","web"]},{"url":"https://github.com/symfony/symfony/releases/tag/v8.0.13","tags":["x_refsource_MISC","Product","Release Notes","web"]},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/mailomat-mailer/CVE-2026-48747.yaml","tags":["web"]},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-48747.yaml","tags":["web"]},{"url":"https://symfony.com/cve-2026-48747","tags":["web"]},{"url":"https://github.com/advisories/GHSA-rrj9-5q2j-4gvr"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48747.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48747","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-48747","tags":["advisory"]},{"url":"https://github.com/symfony/symfony","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-48747","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-48747","tags":["report"]},{"url":"https://symfony.com/blog/cve-2026-48747-mailomat-webhook-parser-reads-the-hmac-algorithm-from-the-request-signature-algorithm-downgrade","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-48747","title":"Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","status":"published","published":"2026-07-14T19:16:24.327Z","modified":"2026-07-15T14:22:53.743Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"}],"cwes":["CWE-347","CWE-757"],"updated_at":"2026-11-02T13:50:49.872037Z"}],"euvd":[{"id":"EUVD-2026-44375","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","status":"published","published":"2026-07-14T19:16:24Z","modified":"2026-07-15T14:22:53Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T18:19:52.740004Z"}],"ghsa":[{"id":"GHSA-rrj9-5q2j-4gvr","title":"Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade","description":"### Description\n\n`Symfony\\Component\\Mailer\\Bridge\\Mailomat\\Webhook\\MailomatRequestParser::validateSignature()` parses the `X-MOM-Webhook-Signature` request header as `algo=signature` and passes the wire-supplied `$algo` directly to `hash_hmac()` when verifying the request against the configured webhook secret. The request therefore selects the HMAC primitive used to authenticate it.\n\nPHP's `hash_hmac()` enforces only that the chosen algorithm is HMAC-compatible. That set still includes primitives with known cryptanalysis (`md4`, `md5`, `ripemd128`, `tiger128,3`, … — e.g. existential forgery of HMAC-MD4, Contini \u0026 Yin, ASIACRYPT 2006). This is the canonical algorithm-confusion shape, analogous to JWT `alg=none` / `alg=HS256` downgrades: any future cryptographic weakness in any HMAC primitive PHP exposes becomes immediately exploitable against a Mailomat webhook receiver, the moment an attacker is in a position to compute a signature for that primitive, without a code change on the Symfony side.\n\nMailomat's [documented webhook security](https://api.mailomat.swiss/docs/#tag/webhook-security) pins SHA-256; the parser did not.\n\n### Resolution\n\n`MailomatRequestParser::validateSignature()` now requires the signature header to be of the form `sha256=\u003chex\u003e` and verifies the signature with HMAC-SHA256 keyed by the configured secret using a constant-time comparison. Any other algorithm declared on the wire (including the HMAC primitives PHP would otherwise accept) is rejected.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/bdfe9fe0d94d33dfaca0bc2fe0b00b54767b0c88) for branch 7.4 (and forward-ported to 8.0 and 8.1).\n\n### Credits\n\nSymfony would like to thank Omar Alshammari, Essam Alanazi and Alwaleed Alshammari for reporting the issue and Nicolas Grekas for providing the fix.","status":"published","published":"2026-06-15T17:32:28Z","modified":"2026-06-15T17:32:28Z","cwes":["CWE-347","CWE-757"],"updated_at":"2026-11-02T14:40:27.329706Z"}],"nvd":[{"id":"CVE-2026-48747","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","status":"published","published":"2026-07-14T20:17:10.08Z","modified":"2026-07-15T15:16:37.08Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/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","level":"medium","assessor":"secondary"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-347","CWE-757"],"updated_at":"2026-11-02T14:12:29.879716Z"}],"osv":[{"id":"CVE-2026-48747","title":"Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","status":"published","published":"2026-07-14T19:16:24.327Z","modified":"2026-10-28T02:30:36.048254597Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-347","CWE-757"],"updated_at":"2026-11-02T15:45:06.701612Z"},{"id":"DEBIAN-CVE-2026-48747","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","status":"published","published":"2026-07-14T20:17:10.08Z","modified":"2026-10-01T03:03:16.032446706Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T15:45:56.444225Z"},{"id":"UBUNTU-CVE-2026-48747","description":"Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 7.4.13 and 8.0.13, MailomatRequestParser::validateSignature() parsed X-MOM-Webhook-Signature as algo=signature and passed the request-selected algorithm to hash_hmac(), allowing a signature algorithm downgrade instead of enforcing Mailomat's documented SHA-256 webhook signature. This issue is fixed in versions 7.4.13 and 8.0.13.","status":"published","published":"2026-07-14T20:17:00Z","modified":"2026-10-17T13:00:23.546690243Z","cvss":[{"version":"4.0","score":6.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T16:56:33.391918Z"},{"id":"GHSA-rrj9-5q2j-4gvr","title":"Symfony: Mailomat Mailer Webhook Parser Reads the HMAC Algorithm from the Request: Signature Algorithm Downgrade","description":"### Description\n\n`Symfony\\Component\\Mailer\\Bridge\\Mailomat\\Webhook\\MailomatRequestParser::validateSignature()` parses the `X-MOM-Webhook-Signature` request header as `algo=signature` and passes the wire-supplied `$algo` directly to `hash_hmac()` when verifying the request against the configured webhook secret. The request therefore selects the HMAC primitive used to authenticate it.\n\nPHP's `hash_hmac()` enforces only that the chosen algorithm is HMAC-compatible. That set still includes primitives with known cryptanalysis (`md4`, `md5`, `ripemd128`, `tiger128,3`, … — e.g. existential forgery of HMAC-MD4, Contini \u0026 Yin, ASIACRYPT 2006). This is the canonical algorithm-confusion shape, analogous to JWT `alg=none` / `alg=HS256` downgrades: any future cryptographic weakness in any HMAC primitive PHP exposes becomes immediately exploitable against a Mailomat webhook receiver, the moment an attacker is in a position to compute a signature for that primitive, without a code change on the Symfony side.\n\nMailomat's [documented webhook security](https://api.mailomat.swiss/docs/#tag/webhook-security) pins SHA-256; the parser did not.\n\n### Resolution\n\n`MailomatRequestParser::validateSignature()` now requires the signature header to be of the form `sha256=\u003chex\u003e` and verifies the signature with HMAC-SHA256 keyed by the configured secret using a constant-time comparison. Any other algorithm declared on the wire (including the HMAC primitives PHP would otherwise accept) is rejected.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/bdfe9fe0d94d33dfaca0bc2fe0b00b54767b0c88) for branch 7.4 (and forward-ported to 8.0 and 8.1).\n\n### Credits\n\nSymfony would like to thank Omar Alshammari, Essam Alanazi and Alwaleed Alshammari for reporting the issue and Nicolas Grekas for providing the fix.","status":"published","published":"2026-06-15T17:32:28Z","modified":"2026-09-10T03:50:50.617414342Z","cwes":["CWE-347","CWE-757"],"updated_at":"2026-11-02T15:46:56.281047Z"}]}}