http4s has 25 CVEs on record. Disclosure cadence is accelerating: 22 in the last 90 days against 3 in the 90 before. The busiest recent month was September 2026 with 20. The median CVSS is 7.5 (high), with 2 rated critical. None have a confirmed exploitation report. The dominant weakness classes are CWE-444 (8) and CWE-400 (6). Most affected products: http4s (13), org.http4s:http4s-ember-core_2.12 (3), blaze (2).
CVEs per month
Last 12 months, by publish date
- Exploited share
- 0% vs 1% corpus
- Median CVSS
- 7.5
- Publish → KEV
- —
- Last 90 days
- 22 prev 3
Products
- http4s 13
- org.http4s:http4s-ember-core_2.12 3
- blaze 2
- org.http4s:http4s-blaze-server_2.13 2
- http4s-scala-xml 1
- org.http4s:blaze-http_2.13 1
Worst active — by depth score
CVE-2026-61741Critical· 9.3http4s-scala-xml provides `EntityDecoder[F, scala.xml.Elem]` instances that parse XML message bodies51CVE-2026-69204Critical· 9.2Http4s is a Scala interface for HTTP services51CVE-2026-69217High· 8.7Http4s is a Scala interface for HTTP services48CVE-2026-69205High· 8.7Http4s is a Scala interface for HTTP services48CVE-2026-69212Medium· 5.9Http4s is a Scala interface for HTTP services45
http4s vulnerabilities
CVEs affecting http4s, newest first. Open any entry for full detail, references, and exploit status.
25 CVEsRSS
CVE-2026-61741Critical· 9.3http4s-scala-xml provides `EntityDecoder[F, scala.xml.Elem]` instances that parse XML message bodies
http4s-scala-xml provides `EntityDecoder[F, scala.xml.Elem]` instances that parse XML message bodies. Prior to versions 0.24.1 and 1.0.0-M39, these decoders used a `javax.xml.parsers.SAXParserFactory` obtained from `SAXParserFactory.newI…
CVE-2026-69217High· 8.7Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/1.1 parser accepts differing duplicate Content-Length headers and uses the last value instead of rejecting the message. When an Ember server is b…
CVE-2026-69215Medium· 6.8Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The CookieJar client middleware uses unanchored substring checks instead of RFC 6265 domain and path matching when deciding whether to attach a stored cookie.…
CVE-2026-69210High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, WebSocket FrameTranscoder.bodyLength rejects extended payload lengths above Integer.MAX_VALUE but permits negative 64-bit lengths. A remote client that comple…
CVE-2026-69218High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, When Ember receives an HTTP/2 HEADERS or PUSH_PROMISE frame without END_HEADERS, H2Connection buffers the header block and subsequent CONTINUATION fragments w…
CVE-2026-69206Medium· 5.9Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, DigestAuth replay protection records lastNc plus one instead of the highest nonce-count value it has accepted. When a legitimate client sends noncontiguous nc…
CVE-2026-88975High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.37 and 1.0.0-M48, Ember’s HTTP/2 read loop parses a frame’s 24-bit declared length but waits to buffer the entire payload before comparing it with SETTINGS_MAX_FRAME_SIZE. An u…
CVE-2026-69205High· 8.7Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HeaderP.parse uses a case-sensitive substring test for the Transfer-Encoding value and decodes header bytes with the platform default charset. Values …
CVE-2026-69203High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, An Ember server with HTTP/2 enabled through withHttp2 does not enforce SETTINGS_MAX_CONCURRENT_STREAMS for peer-created streams. One unauthenticated connectio…
CVE-2026-69202High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s HTTP/2 flow-control window is replenished according to bytes received from the network rather than bytes consumed by the application, while each strea…
CVE-2026-69216Medium· 5.4Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember’s chunk decoder trims the chunk-size token and accepts leading plus or minus signs instead of requiring one or more hexadecimal digits followed by the r…
CVE-2026-69214Medium· 6.8Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The CookieJar client middleware stores a response cookie’s Domain attribute without checking that it domain-matches the host that supplied the cookie or rejec…
CVE-2026-69213High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can c…
CVE-2026-69212Medium· 5.9PoCHttp4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The FollowRedirect client middleware strips Authorization and Cookie headers only when a redirect changes authority, but authority comparison excludes the URI…
CVE-2026-69211Medium· 4.8Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, ResponseCookie.render writes attacker-influenced name, content, domain, path, and extension values without neutralizing semicolons or control characters. An a…
CVE-2026-69209High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The shared WebSocket decoder permits unbounded message buffering because defragmentation accumulates fragments without a limit and FrameTranscoder accepts dec…
CVE-2026-69208High· 7.5Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, the DigestAuth server middleware removes fresh nonces and stops eviction at the first stale nonce because its stale-nonce comparison is inverted. On an applic…
CVE-2026-69204Critical· 9.2Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/1.1 does not reject messages containing both Transfer-Encoding and Content-Length, so an intermediary and Ember can select different body framing r…
CVE-2026-69201Medium· 5.9Http4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, ResourceService and WebjarService decode each URL path segment but reject only segments exactly equal to an empty string, a dot, or two dots. A request contai…
CVE-2026-73494High· 7.4blaze is a Scala library for building asynchronous pipelines, with a focus on network IO
blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and from 1.0.0-M1 until 1.0.0-M42, five HTTP/1.1 conformance laxities in the hand-written Java parser under http/src/main/java/org…
CVE-2026-54556HighHttp4s is a Scala interface for HTTP services
Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, an unauthenticated HTTP/2 peer can cause an out-of-memory denial of service in the Ember backend with HTTP/2 enabled. The Hpack wrapper in ember-core/shared/s…
CVE-2026-73495High· 7.4blaze is a Scala library for building asynchronous pipelines, with a focus on network IO
blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and 1.0.0-M42, blaze-server can merge HTTP/1.1 chunked-body trailer fields into Request.headers. Because trailer fields are attack…
GHSA-mhvj-jhpq-885vHigh· 7.4blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
GHSA-46q4-43ph-c6frHigh· 7.4blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)
blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)
GHSA-7ppr-r889-mcf2High· 7.5blaze: Unbounded WebSocket message aggregation in http4s-blaze-server
blaze: Unbounded WebSocket message aggregation in http4s-blaze-server